Digital multifunction reprographic systems have grown in sophistication and function. Digital multifunction reprographic systems include a variety of options to improve the image quality of output documents and in addition they are often used in networked environments. The improved image processing means that a variety of halftones and tone response curves may be applied to the data to be printed.
The networked environment makes it possible for a document to be RIPed at one machine and printed on another, remote, machine. The document to be printed is often rasterized into a binary representation of the pages to be printed before transmission to the remote machine.
In such a case where the document is binarized at one location and printed remotely, the remote machine would produce higher quality pictorials had it been able to use the proper tone response curve for each halftone that is applied to the document. If this information is not supplied with the binary document representation, it would be desirable for the remote machine to be able to reliably identify the halftones present in the document to be printed. This identification is required in order to accommodate a subsequent halftone frequency dependent tone response curve adjustment.
In another application, customers might choose to adjust the appearance of a printed document with a change in the darkness or contrast level. To achieve consistent results across a range of possible halftone frequency candidates, a distinctly different tone response adjustment curve is needed; one for each supported halftone frequency candidate.
In another application, customers might choose to adjust the appearance of a printed document with a different level of change in text and halftone pictorial areas. To darken or lighten text without adjusting pictorials, adjust pictorials only, or to darken one while lightening another (or to a different degree), identifying pictorial from text and line-art is a necessary first step.
Therefore, it is desirable to provide a real-time imbedded halftone frequency detection algorithm to distinguish between a series of distinct halftone frequencies of interest and text when there is no tag plane available to identify these to the print engine.